Infants with persistent pulmonary hypertension (PPHN) are among the most critically ill patients cared for in the Neonatal Intensive Care Unit and are at significant risk for neurodevelopmental abnormalities related to their primary illness as well as a consequence of the therapies used to keep them alive. Currently, we approach these infants with several different sequential therapies, which include conventional medical therapy (CMT) with high frequency ventilation and induction of alkalosis, inhaled nitric oxide therapy (INO) and extracorporeal membrane oxygenation (ECMO). Despite the life-saving benefits of these therapies and encouraging survival statistics, both conventional medical therapy and ECMO are not without significant long-term neurodevelopmental sequelae. Early studies have demonstrated that 70% of ECMO survivors have mean IQ scores in the normal range and a low incidence of major handicapping conditions given the critical perinatal illness of the infants. However, these children were found by us and others to have a disturbing number of neurodevelopmental deficits suggesting that they are at substantial risk for subtle cognitive and behavioral problems that influence later academic and psychosocial adjustment. The outcome following INO, an investigational new drug, has not yet been documented. To date, the risk, benefits and outcome of conventional medical therapy in comparison to INO and ECMO have not been systematically assessed. The purpose of this study is to understand the abnormalities of growth and neurodevelopment in infants with neonatal pulmonary hypertension and to determine if these abnormalities differ amongst patients who receive differing therapies for pulmonary hypertension. A multidisciplinary evaluation will be conducted in the Mary L. Johnson Infant Development Clinic through age 7. Standard broad based testing will be utilized to evaluate physical and neurologic outcome, with more detailed assessments of hearing, speech/language development, higher cortical functioning and minor neuromotor development. Longitudinal outcome data for the different treatment groups will be analyzed to determine if there are distinct outcomes.